The present invention relates to a process and to an apparatus for the electrolytic treatment of solutions containing tritiated water, such as effluents from irradiated nuclear fuel reprocessing plants, cooling water from light or heavy water nuclear reactors and effluents from laboratories where tritium is handled.
In irradiated nuclear fuel reprocessing installations, at certain stages of the reprocessing process, aqueous solutions are obtained which contain a large amount of tritiated water, e.g. approximately 40 Ci/m.sup.3. These solutions are generally obtained during the concentration by evaporation of solutions of uranium, plutonium or fission products, or during the regeneration processing of nitric acid with a view to its recycling during the dissolving of irradiated fuel elements. In the latter case, these solutions are obtained during the concentration of nitric acid formed on regenerating, by means of water vapour or steam, the oxides of nitrogen from the destruction of the nitric acid by formol. It is also possible to envisage higher concentrations, either by recycling nitric solutions, or by isotopic concentration of the effluents.
At present, no process is known which makes it possible to ensure, under satisfactory conditions, a processing of the tritiated water with a view to recovering the tritium contained therein. Thus, the methods involving chemical reduction of the tritiated water by means of uranium in the hot state have the disadvantage of consuming uranium and leading to uranium oxide waste contaminated by tritium. Moreover, it is very difficult to handle tritiated water and numerous contamination problems are caused.
Consideration has been given to the use of an electrolytic process for treating effluents containing tritiated water from a carbon dioxide gas-cooled nuclear reactor, as described in DE-A 1,965,627 filed by Atomic Power Constructions Limited. However, according to this process, it is not possible to recover the tritium given off to the cathode with a high degree of purity, because gaseous impurities such as steam and oxygen are still contained. Moreover, this process does not make it possible to obtain good tritium yields.